The present invention relates to the feeding of rod-like articles, such as cigarettes, to magazines or hoppers from which the articles are fed to a manipulating machine, such as a cigarette packing machine. The said feeding is usually performed by emptying into the hopper the so-called trays, which are in the form of containers having the shape of parallelepipeds open at two adjacent sides, inside which the articles are arranged side-by-side in superposed rows.
There are known devices in which the full tray is introduced into a holder frame which closes its open sides and then is turned upside down onto the hopper. The cigarettes are then discharged from the tray into the hopper by opening the discharge side of the tray. Level sensing means are provided which sense the level of the cigarettes in correspondence with the inlet mouth of the hopper, and generate a control signal for the substitution of the emptied tray with a new full tray.
Between the moment in which the said control signal for the substitution of the emptied tray is given, and the moment in which the discharge side of the newly-placed full tray is opened, there passes a certain period of time, during which the level of the articles in the hopper continues to decrease, due to the uninterrupted operation of the cigarette packing machine which receives the articles from the hopper.
As a consequence, when the discharge side of the full tray is opened, the discharged cigarettes effect a free drop, the length of which depends on the speed of the packing machine and on the period of time required for the substitution of the trays. This free drop of the cigarettes into the hopper should be avoided, since it can be detrimental to the orderly arrangement of the cigarettes in the hopper itself, and consequently to the operation of the cigarette packing machine.
In order to avoid this inconvenience, there have been studied devices which greatly reduce the periods of time required for the substitution of an empty tray with a full tray, and for the actual starting of the discharge of the cigarettes from the newly placed full tray into the hopper. The problem however remains, as a consequence of the present utilization of the so-called high speed packing machines, whereby, even if the tray substitution time is very short, the level of cigarettes in the hopper during said time decreases in a considerable manner, and the actual length of the free drop of the cigarettes at the opening of the discharge side of the full tray is remarkable.